Tellurium dioxide is the most widely used uniaxial crystal for acousto-optic devices. Acousto-optic tunable filters based on this material can cover spectral range from UV to MWIR in a non-collinear configuration. The diffracted narrow band output beams have orthogonal linear polarizations, propagating in different directions, allowing the filter to act as polarizing beam splitter/analyzer as well. To achieve full electronic tuning, two liquid crystal variable retarders are used to measure all six polarization states used in the calculation of Stokes vector. We will present the design of the instrument, test results, and performance considerations.

We report on the development of an acousto-optic tunable filter (AOTF) based novel, high speed spectropolarimeter system operating over the visible and near-IR spectral bands to extract Stokes and Mueller matrices. Developed primarily for planetary composition and analysis applications, the wavelength tunable polarimetric system is configured with tellurium dioxide based AOTF and liquid crystal based variable retarders (LCVR) with no movable mechanical parts. Fitted with a standard silicon camera for operation up to 900 nm and a Mercury Cadmium Telluride (MCT) camera for operation up to 2500 nm, the spectropolarimetric system is currently configured for passive operation. The operation of this spectropolarimetric system is fully automated with an interactive and user friendly graphical user interface, and accordingly provides a snapshot polarimetric measurement capability in minutes.

The transition metal oxide embodied organic composites have great promise for high energy radiation detection. The interaction of high energy radiation such as &gamma;-rays with the organic composite can generate photoelectric responses, Compton scattering and electron hole pairs, which can provide favorable properties to enhance the radiation detectivity of the composite. These effects along with changes of oxidation state of metal oxides, provide significant change in the electrical characteristics of composites due to radiation exposure. We have developed nickel oxide (NiO2) nanoparticles embodied urea composite (urea-NiO<sub>2</sub>), and determined effect of &gamma;-radiation on the current – voltage characteristics in the frequency range of 100 Hz to 100,000Hz. In this paper, we describe the results of effect of additional oxidizing agent MnO<sub>2</sub> (urea-NiO<sub>2</sub>-MnO<sub>2</sub>) on the morphology, processing and current voltage characteristics due to exposure of Cs-137 &gamma;-radiation. It was observed that addition of MnO<sub>2</sub> in urea-NiO<sub>2</sub> composite decreases the sensitivity of detection. However, urea-NiO<sub>2</sub>-MnO<sub>2</sub> composite recovers to original properties after irradiation much faster than urea-NiO<sub>2</sub> composite.

We have developed ultra-low noise quadrant InGaAs photoreceivers for multiple applications ranging from Laser Interferometric Gravitional Wave Detection, to 3D Wind Profiling. Devices with diameters of 0.5 mm, 1mm, and 2 mm were processed, with the nominal capacitance of a single quadrant of a 1 mm quad photodiode being 2.5 pF. The 1 mm diameter InGaAs quad photoreceivers, using a low-noise, bipolar-input OpAmp circuitry exhibit an equivalent input noise per quadrant of &lt;1.7 pA/√Hz in 2 to 20 MHz frequency range. The InGaAs Quad Photoreceivers have undergone the following reliability tests: 30 MeV Proton Radiation up to a Total Ionizing Dose (TID) of 50 krad, Mechanical Shock, and Sinusoidal Vibration.

The hexagonal apatite single crystals have been investigated for their applications as laser host materials. Czochralksi and flux growth methods have been utilized to obtain single crystals. For low temperature processing (&lt;100 <sup>0</sup>C), several techniques for crystal growth have been developed. The hexagonal apatite structure (space group P<sup>6</sup>3/m) is characteristic of several compounds, some of which have extremely interesting and useful properties as laser hosts and bone materials. Calcium lanthanum silicate (Nd-doped) and lanthanum aluminate material systems were studied in detail. Nanoengineered calcium and lanthanum based silicates were synthesized by a solution method and their optical and morphological characteristics were compared with Czochralski grown bulk hydroxyapatite single crystals. Materials were evaluated by absorbance, fluorescence and Raman characteristics. Neodymium, iron and chromium doped crystals grown by a solution method showed weak but similar optical properties to that of Czochralski grown single crystals.

We present a mathematical approach to appreciate that short pulse characterization requires recognizing inseparability of the measurements of the amplitude envelope-correlation and spectral measurements and then use a suitable iterative approach to derive the real characteristics. We will use a standard Michelson interferometer, as usual, to introduce the autocorrelation function of a pulse containing single and multiple frequencies. In the process, we also underscore that detectors play the key role in generating measurable Superposition Effects (SE), recognized as fringes after the detectors carry out the square modulus operation. Simple mathematical summation of amplitude factors, the Superposition Principle (SP), is not directly observable. We underscore this by mentioning that we present EM waves as classical and detectors as quantum mechanical. This semi-classical approach has been established by Lamb and Jaynes, which is indirectly supported by Glauber’s comment, “A photon is what a detector detects”. The semi-classical approach helps us separate the phenomenological difference between the absorbed detected energy by a detector (SE) from the energy supplied by the simultaneously present multiple wave amplitudes (SP). As in atomic and molecular physics, we use the detector’s dipolar stimulation as the product of its linear dipolar polarizability multiplied by all the EM fields stimulating it simultaneously. The analysis also demonstrates that for a pulse containing multiple frequencies, the two-beam autocorrelation function becomes a product of the traditional amplitude correlation factor and a frequency-comb correlation factor. Hence, the spectral interpretation of a short pulse and two-beam autocorrelation are inseparable. Therefore, the detailed characterization would require iterative computational approach by guessing the most plausible functional forms. This deeper understanding can be applied to rapid re-calibration of pulsed lasers that need to be maintained at single mode but has the tendency to move to multimode behavior. If the newly measured autocorrelation function differs from the original amplitude correlation factor, then one should check for the spectral characteristics first, before assuming that only the pulse shape has changed.

Lead selenide (PbSe) has been studied as a promising material for room temperature midwave infrared detection. We have investigated pure PbSe, as well as tin (Tn) and cadmium (Cd)-doped PbSe, nanocrystalline materials produced using physical vapor transport methods on glass and high-resistivity silicon substrates. The morphologies were investigated by scanning electron microscopy and energy-dispersive x-ray analysis. Pure PbSe layers consisted of nanocrystals that change into cubes and cuboids upon annealing. Cuboids generally grew in [100] orientation and ultimately developed in nanorods. Growth on silicon and glass substrates showed different morphologies of pure PbSe material. Parabolic and elongated morphologies resulted in nanowires on the top of thin layers of PbSe nanofilm, which acted as the substrate. Under low gradient annealing conditions (<20 K/cm), elongated morphologies grew into nanorods. Annealing of these samples resulted in coarse nanomorphologies with higher resistivity. In the case of Tn-doped PbSe, annealing dissolved a Tn-rich phase observed in as-grown films. Cd- and iodine-doped films produced through the addition of Cd selenide and Cd iodide, respectively, showed higher resistivity than similarly treated pure PbSe films. Annealing of as-grown materials in the presence of oxygen or iodine showed increased resistivity and significant changes in optical characteristics.

The development of a three-beam aerosol backscatter correlation (ABC) light detection and ranging (lidar) to measure wind characteristics for wake vortex and plume tracking applications is discussed. This is a direct detection elastic lidar that uses three laser transceivers, operating at 1030-nm wavelength with ∼10-kHz pulse repetition frequency and nanosec class pulse widths, to directly obtain three components of wind velocities. By tracking the motion of aerosol structures along and between three near-parallel laser beams, three-component wind speed profiles along the field-of-view of laser beams are obtained. With three 8-in. transceiver modules, placed in a near-parallel configuration on a two-axis pan–tilt scanner, the lidar measures wind speeds up to 2 km away. Optical flow algorithms have been adapted to obtain the movement of aerosol structures between the beams. Aerosol density fluctuations are cross-correlated between successive scans to obtain the displacements of the aerosol features along the three axes. Using the range resolved elastic backscatter data from each laser beam, which is scanned over the volume of interest, a three-dimensional map of aerosol density can be generated in a short time span. The performance of the ABC wind lidar prototype, validated using sonic anemometer measurements, is discussed.

Deep space radiations pose a major threat to the astronauts and their spacecraft during long duration space exploration missions. The two sources of radiation that are of concern are the galactic cosmic radiation (GCR) and the short lived secondary neutron radiations that are generated as a result of fragmentation that occurs when GCR strikes target nuclei in a spacecraft. Energy loss, during the interaction of GCR and the shielding material, increases with the charge to mass ratio of the shielding material. Hydrogen with no neutron in its nucleus has the highest charge to mass ratio and is the element which is the most effective shield against GCR. Some of the polymers because of their higher hydrogen content also serve as radiation shield materials. Ultra High Molecular Weight Polyethylene (UHMWPE) fibers, apart from possessing radiation shielding properties by the virtue of the high hydrogen content, are known for extraordinary properties. An effective radiation shielding material is the one that will offer protection from GCR and impede the secondary neutron radiations resulting from the fragmentation process. Neutrons, which result from fragmentation, do not respond to the Coulombic interaction that shield against GCR. To prevent the deleterious effects of secondary neutrons, targets such as Gadolinium are required. In this paper, the radiation shielding studies that were carried out on the fabricated sandwich panels by vacuum-assisted resin transfer molding (VARTM) process are presented. VARTM is a manufacturing process used for making large composite structures by infusing resin into base materials formed with woven fabric or fiber using vacuum pressure. Using the VARTM process, the hybridization of Epoxy/UHMWPE composites with Gadolinium nanoparticles, Boron, and Boron carbide nanoparticles in the form of sandwich panels were successfully carried out. The preliminary results from neutron radiation tests show that greater than 99% shielding performance was achieved with these sandwich panels. Moreover, the mechanical testing and thermo-physical analysis performed show that core materials can preserve their thermo-physical and mechanical integrity after radiation.

Recently, a mercury-cadmium-telluride (MCT) linear array detection system that is capable of rapidly capturing (~1-5 second) a broad spectrum of atomic and molecular laser-induced breakdown spectroscopy (LIBS) emissions in the longwave infrar&mu;ed region (LWIR, ~5.6 to 10 &mu;m) has been developed. Similar to the conventional Ultraviolet (UV)-Visible (Vis) LIBS, a broad band emission spectrum of condensed phase samples covering the entire 5.6 to 10 &mu;m region can be acquired from just a single laser-induced micro-plasma or averaging a few single laser-induced micro-plasmas. This setup has enabled probing samples “as is” without the need for extensive sample preparation and also offers the possibility of a simultaneous UV-Vis and LWIR LIBS measurement. A Martian regolith simulant (JSC Mars-1A) was studied with this novel Vis + LWIR LIBS array system. A broad SiO<sub>2</sub> vibrational emission feature around 9.5 &mu;m and multiple strong emission features between 6.5 to 8 &mu;m can be clearly identified. The 6.5 to 8 &mu;m features are possibly from biological impurities of the simulant. JSC Mars-1A samples with organic methyl salicylate (MeS, wintergreen oil) and Dimethyl methyl-phosphonate (DMMP) residues were also probed using the LWIR LIBS array system. Both molecular spectral signature around 6.5 &mu;m and 9.5 &mu;m of Martian regolith simulant and MeS and DMMP molecular signature emissions, such as Aromatic CC stretching band at 7.5 &mu;m, C-CH<sub>3</sub>O asymmetric deformation at 7.6 &mu;m, and P=O stretching band at 7.9 &mu;m, are clearly observed from the LIBS emission spectra in the LWIR region.

This paper describes an innovative, compact and eyesafe coherent lidar system developed for use in wind and wake vortex sensing applications. This advanced lidar system is field ruggedized with reduced size, weight, and power consumption (SWaP) configured based on an all-fiber and modular architecture. The all-fiber architecture is developed using a fiber seed laser that is coupled to uniquely configured fiber amplifier modules and associated photonic elements including an integrated 3D scanner. The scanner provides user programmable continuous 360 degree azimuth and 180 degree elevation scan angles. The system architecture eliminates free-space beam alignment issues and allows plug and play operation using graphical user interface software modules. Besides its all fiber architecture, the lidar system also provides pulsewidth agility to aid in improving range resolution. Operating at 1.54 microns and with a PRF of up to 20 KHz, the wind lidar is air cooled with overall dimensions of 30” x 46” x 60” and is designed as a Class 1 system. This lidar is capable of measuring wind velocities greater than 120 +/- 0.2 m/s over ranges greater than 10 km and with a range resolution of less than 15 m. This compact and modular system is anticipated to provide mobility, reliability, and ease of field deployment for wind and wake vortex measurements. The current lidar architecture is amenable for trace gas sensing and as such it is being evolved for airborne and space based platforms. In this paper, the key features of wind lidar instrumentation and its functionality are discussed followed by results of recent wind forecast measurements on a wind farm.

Recently, Non- Interaction of Waves or the NIW property has been proposed as a generic property of all propagating electromagnetic waves by one of the authors (CR). In other words, optical beams do not interact with each other to modify or re-distribute their field energy distribution in the absence of interacting materials. In this paper, path taken to re-create CR's original demonstration of the NIW-property as an on-site tabletop experiment is discussed. Since 1975, when the NIW demonstration was first reported, several advances in lasers and optical component design architecture have occurred. With the goal of using low cost components and having agility in setting up on non-conformable platforms for general viewing, a compact arrangement for demonstrating the NIW property was envisioned. In our experimental arrangement, a beam multiplier element was utilized to generate a set of spatially separate parallel beams out of an incident laser beam. The emerging parallel beams from the beam multiplier element were then focused on a one-sided ground glass, the flat side being towards the beam multiplier. This flat side reflects off all the incident focused beams as fanning out independent laser beams, remaining unperturbed even though they are reflecting out of a common superposed spot. It is clear that there is neither "interference between different photons", nor "a photon interferes with itself", even within a region of superposed beams. In contrast, the ground glass surface (same silica molecules but granular or lumpy) was anticipated to generate a set of crisp spatial fringes on its surface as in the original experiment. The fringes are due to granulated individual silica lumps responding simultaneously to the local resultant E-vectors due to all the superposed beams and are scattering energy proportional to the square modulus of the sum of all the simultaneous dipolar amplitude stimulations. The dark fringe locations imply zero resultant amplitude stimulation and hence no scattering. Due to multi-longitudinal mode nature of laser module, the fringes appeared washed out at the backside of the ground glass plate. Experimental refinements followed by our views on whether the fundamental physics behind the generation of superposition fringes by photo detectors different from those due to a ground glass are briefly discussed.

This paper discusses an innovative, compact and eyesafe coherent lidar system developed for wind and wake vortex sensing applications. With an innovative all-fiber and modular transceiver architecture, the wind lidar system has reduced size, weight and power requirements, and provides enhanced performance along with operational elegance. This all-fiber architecture is developed around fiber seed laser coupled to uniquely configured fiber amplifier modules. The innovative features of this lidar system, besides its all fiber architecture, include pulsewidth agility and user programmable 3D hemispherical scanner unit. Operating at a wavelength of 1.5457 microns and with a PRF of up to 20 KHz, the lidar transmitter system is designed as a Class 1 system with dimensions of 30”(W) x 46”(L) x 60”(H). With an operational range exceeding 10 km, the wind lidar is configured to measure wind velocities of greater than 120 m/s with an accuracy of +/- 0.2 m/s and allow range resolution of less than 15 m. The dynamical configuration capability of transmitted pulsewidths from 50 ns to 400 ns allows high resolution wake vortex measurements. The scanner uses innovative liquid metal slip ring and is built using 3D printer technology with light weight nylon. As such, it provides continuous 360 degree azimuth and 180 degree elevation scan angles with an incremental motion of 0.001 degree. The lidar system is air cooled and requires 110 V for its operation. This compact and modular lidar system is anticipated to provide mobility, reliability, and ease of field deployment for wind and wake vortex measurements. Currently, this wind lidar is undergoing validation tests under various atmospheric conditions. Preliminary results of these field measurements of wind characteristics that were recently carried out in Colorado are discussed.

The search for improved thermoelectric materials is driven in part by the desire to convert otherwise wasted lowtemperature heat into useful electricity. In this work, we demonstrate a new path towards materials having higher overall zT, and consequently improved capacity to obtain more electrical power from a given content of heat. We produced alloys of (Bi,Sb)<sub>2</sub>Te<sub>3</sub> using a special gas atomization process that is capable of producing source powder material having nanometer-scale grain size. When impulse-compacted by shockwave consolidation, the obtained dense solid will retain its nanostructure because insufficient time and temperature are available for the kinetics of any appreciable grain growth to proceed. However, if there is initial non-uniformity in the properties of the source powder, or if there is stress non-symmetries during shockwave consolidation, then the obtained consolidated material may have locally inhomogeneous properties distributed throughout the material. Thermoelectric property measurements from selected regions within the consolidated sample indicate a wide distribution of properties. For example, the thermal conductivity at room temperature ranged from as low as 1.30 Watts/m-K in one region to higher than 3.00 Watts/m-K in a neighboring region. The electrical resistivity showed similar variation from as low as 0.5 m&Omega;-cm to as high as 1.5 m&Omega;-cm. Individually, those regions exhibited thermoelectric material figure-of-merit, zT values ranging between 0.3 and 0.4. However, when combined into a dense nanocomposite, the overall ensemble zT approaches 0.7 which is nearly a factor of 2 higher.

A great deal of research has been performed on developing room temperature mid wave infrared (MWIR) and long wave infrared (LWIR) detectors to replace very costly mercury cadmium telluride based detectors. Among the more studied materials for high operating temperature detectors, PbSe and PbSe-type heavy metal selenides have been grown in the bulk, thin film and nano crystal morphologies. To better understand the effects of the substrate on the properties of these thin films, we have deposited lead selenide by physical vapor transport (PVT) method on highresistivity Si substrates and studied the characteristics of the film. Growth on silicon and glass substrates showed different morphologies compared to pure lead selenide material. It was seen that materials grown on a glass substrate possessed different morphology after annealing. FTIR was used to calculate bandgap information comparison with undoped PbSe. We will describe the details of the growth method, effect of substrate on nucleation and morphology of the pure and lead selenide material and band gap comparisons between substrates.

The objective of the Materials International Space Station Experiment (MISSE) is to study the performance of novel materials when subjected to the synergistic effects of the harsh space environment for several months. MISSE missions provide an opportunity for developing space qualifiable materials. Several laser and lidar components were sent by NASA Langley Research Center (LaRC) as a part of the MISSE 7 mission. The MISSE 7 module was transported to the
international space station (ISS) via STS 129 mission that was launched on Nov 16, 2009. Later, the MISSE 7 modulewas brought back to the earth via the STS 134 that landed on June 1, 2011. The MISSE 7 module that was subjected to exposure in space environment for more than one and a half year included fiber laser, solid-state laser gain materials, detectors, and semiconductor laser diode. Performance testing of these components is now progressing. In this paper,
the results of performance testing of a laser diode module sent by NASA Langley Research Center on MISSE 7 mission will be discussed. This paper will present the comparison of pre-flight and post-flight performance of two different COTS acousto-optic modulator devices. Post-flight measurements indicate that these two devices did not undergo any significant performance degradation.

Nanotechnology based thermoelectric materials are considered attractive for developing highly efficient thermoelectric
devices. Nano-structured thermoelectric materials are predicted to offer higher ZT over bulk materials by reducing
thermal conductivity and increasing electrical conductivity. Consolidation of nano-structured powders into dense
materials without losing nanostructure is essential towards practical device development. Using the gas atomization
process, amorphous nano-structured powders were produced. Shockwave consolidation is accomplished by surrounding
the nanopowder-containing tube with explosives and then detonated. The resulting shock wave causes rapid fusing of
the powders without the melt and subsequent grain growth. We have been successful in generating consolidated nanostructured
bismuth telluride alloy powders by using shockwave technique. Using these consolidated materials, several
types of thermoelectric power generator devices have been developed. Shockwave consolidation is anticipated to
generate large quantities of nanostructred materials expeditiously and cost effectively. In this paper, the technique of
shockwave consolidation will be presented followed by Seebeck Coefficient and thermal conductivity measurements of
consolidated materials. Preliminary results indicate a substantial increase in electrical conductivity due to shockwave
consolidation technique.

In this paper, we describe the development of a three-beam elastic lidar that utilizes aerosol backscatter correlation to measure three-component wind profiles for detecting and tracking aircraft wake vortices; turbulence intensity and wind shear profiles. High-resolution time-resolved wind information can currently be obtained with ultrasonic or hot-wire anemometers suitable for local point measurements, or with Doppler wind lidars that only measure line-of-sight wind speeds and have to be scanned over large measurement cone angles for obtaining three-component winds. By tracking the motion of aerosol structures along and between three near-parallel laser beams, our lidar obtains three-component wind speed profiles along the field of view (FOV) of the lidar beams. Our prototype lidar wind profiler (LWP) has three 8-inch transceiver modules placed in a near-parallel configuration on a two-axis pan-tilt scanner to measure winds up to 2km away. Passively q-switched near-infrared (1030nm) Yb:YAG lasers generate 12 - 18ns wide pulses at high repetition rate (about 10KHz) that are expanded and attenuated to eye-safe levels. Sensitive low noise detection is achieved even in daytime using a narrow FOV receiver, together with narrowband interference filters and single photoncounting Geiger-mode Si detectors. A multi-channel scaler retrieves the lidar return with 7.8ns bins (∼1.2m spatial resolution) and stores accumulated counts once every 50ms (20 profiles/sec). We adapted optical flow algorithms to obtain the movement of aerosol structures between the beams. The performance of our prototype LWP was validated using sonic anemometer measurements.

The NIW (non-interaction of waves) property has been proposed by one of the coauthors. The NIW property states that in the absence of any “obstructing” detectors, all the Huygens-Fresnel secondary wave lets will continue to propagate unhindered and without interacting (interfering) with each other. Since a coherent lidar system incorporates complex behaviors of optical components with different polarizations including circular polarization for the transmitted radiation, then the question arises whether the NIW principle accommodate elliptical polarization of light. Elliptical polarization presumes the summation of orthogonally polarized electric field vectors which contradicts the NIW principle. In this paper, we present working of a coherent lidar system using Jones matrix formulation. The Jones matrix elements represent the anisotropic dipolar properties of molecules of optical components. Accordingly, when we use the Jones matrix methodology to analyze the coherent lidar system, we find that the system behavior is congruent with the NIW property.

Optical beam alignment in a coherent lidar (or ladar) receiver system plays a critical role in optimizing its performance. Optical alignment in a coherent lidar system dictates the wavefront curvature (phase front) and Poynting vector) matching of the local oscillator beam with the incoming receiver beam on a detector. However, this alignment is often not easy to achieve and is rarely perfect. Furthermore, optical fibers are being increasingly used in coherent lidar system receivers for transporting radiation to achieve architectural elegance. Single mode fibers also require stringent mode matching for efficient light coupling. The detector response characteristics vary with the misalignment of the two pointing vectors. Misalignment can lead to increase in DC current. Also, a lens in front of the detector may exasperate phase front and Poynting vector mismatch. Non-Interaction of Waves, or the NIW property indicates the light beams do not interfere by themselves in the absence of detecting dipoles. In this paper, we will analyze the extent of misalignment on the detector specifications using pointing vectors of mixing beams in light of the NIW property.

The objective of the Materials International Space Station Experiment (MISSE) is to study the performance of novel materials when subjected to the synergistic effects of the harsh space environment for several months. MISSE missions provide an opportunity for developing space qualifiable materials. Several laser and lidar components were sent by NASA Langley Research Center (LaRC) as a part of the MISSE 7 mission. The MISSE 7 module was transported to the international space station (ISS) via STS 129 mission that was launched on Nov 16, 2009. Later, the MISSE 7 module was brought back to the earth via the STS 134 that landed on June 1, 2011. The MISSE 7 module that was subjected to exposure in space environment for more than one and a half year included fiber laser, solid-state laser gain materials, detectors, and semiconductor laser diode. Performance testing of these components is now progressing. In this paper, the results of performance testing of a laser diode module sent by NASA Langley Research Center on MISSE 7 mission will be discussed. This paper will present the comparison of pre-flight and post-flight performance curves and discuss the effect of space exposure on the laser diode module. Preliminary findings on output power measurements show that the COTS laser diode characteristics did not undergo any significant performance degradation.

We report on recent progress made in the development of highly compact, single mode, distributed
feedback laser (DFB) seed laser modules with integrated drive electronics for lidar and spectroscopy
applications from space based platforms. One of the intended application of this technology is in the
NASA’s Active Sensing of CO<sub>2</sub> Emissions over Nights, Days, and Seasons (ASCENDS) mission.
NASA Langley Research Center (LaRC) is working on a prototype laser based spectroscopy system
for simultaneous measurement of CO<sub>2</sub> and O<sub>2</sub> for planned Active Sensing of CO<sub>2</sub> Emissions over Nights, Days, and Seasons (ASCENDS) mission application. For this purpose, 1571 nm spectral
band for CO<sub>2</sub> sensing and 1262 nm spectral band for oxygen sensing have been selected. In this
paper, we discuss recent progress made in the development of single mode, compact and stable, seed
laser technologies for CO<sub>2</sub> and O<sub>2</sub> transmitters with focus on linewidth and noise measurements. The
1571 nm and 1262 nm DFB laser modules with integrated drive electronics have advanced current
and temperature drivers built into them. A combination of temperature and current tuning allows
coarse and fine adjustment of the diode wavelengths. The current tuning was demonstrated at a rate
of ~0.7 pm/mV over a working range of ~1 V for a total of 0.7 nm. Also, temperature tuning at a
rate of ~2 pm/mV over a working range of ~1 V for a total wavelength range of ~2 nm was
demonstrated. The current tuning was performed at a rate of up to 200 kHz allowing rapid
adjustment and dithering of the laser frequency. Furthermore, the best performance of laser
linewidth observed was ~11 kHz with frequency stability &lt;10 MHz over 1 hour period. The microcooler
arrangement embedded inside these modules has provided significant reduction in power
consumption. The electronics has been designed, prototyped and tested using space-qualified
components within a hermetically sealed package of volume less than 2" x 2" x 0.5".

We performed comparative studies to establish favorable spectral regions and measurement wavelength combinations in
alternative bands of CO2 and O2, for the sensing of CO2 mixing ratios (XCO2) in missions such as ASCENDS. The
analysis employed several simulation approaches including separate layers calculations based on pre-analyzed
atmospheric data from the modern-era retrospective analysis for research and applications (MERRA), and the line-by-line
radiative transfer model (LBLRTM) to obtain achievable accuracy estimates as a function of altitude and for the
total path over an annual span of variations in atmospheric parameters. Separate layer error estimates also allowed
investigation of the uncertainties in the weighting functions at varying altitudes and atmospheric conditions. The
parameters influencing the measurement accuracy were analyzed independently and included temperature sensitivity,
water vapor interferences, selection of favorable weighting functions, excitations wavelength stabilities and other
factors. The results were used to identify favorable spectral regions and combinations of on / off line wavelengths
leading to reductions in interferences and the improved total accuracy.

Current approaches to satellite observation data storage and distribution implement separate visualization and data access methodologies which often leads to the need in time consuming data ordering and coding for applications requiring both visual representation as well as data handling and modeling capabilities. We describe an approach we implemented for a data-encoded web map service based on storing numerical data within server map tiles and subsequent client side data manipulation and map color rendering. The approach relies on storing data using the lossless compression Portable Network Graphics (PNG) image data format which is natively supported by web-browsers allowing on-the-fly browser rendering and modification of the map tiles. The method is easy to implement using existing software libraries and has the advantage of easy client side map color modifications, as well as spatial subsetting with physical parameter range filtering. This method is demonstrated for the ASTER-GDEM elevation model and selected MODIS data products and represents an alternative to the currently used storage and data access methods. One additional benefit includes providing multiple levels of averaging due to the need in generating map tiles at varying resolutions for various map magnification levels. We suggest that such merged data and mapping approach may be a viable alternative to existing static storage and data access methods for a wide array of combined simulation, data access and visualization purposes.

Studies were performed to carry out semi-empirical validation of a new measurement approach we propose for
molecular mixing ratios determination. The approach is based on relative measurements in bands of O<sub>2</sub> and other
molecules and as such may be best described as cross band relative absorption (CoBRA). The current validation
studies rely upon well verified and established theoretical and experimental databases, satellite data assimilations and
modeling codes such as HITRAN, line-by-line radiative transfer model (LBLRTM), and the modern-era retrospective
analysis for research and applications (MERRA). The approach holds promise for atmospheric mixing ratio
measurements of CO<sub>2</sub> and a variety of other molecules currently under investigation for several future satellite lidar
missions. One of the advantages of the method is a significant reduction of the temperature sensitivity uncertainties
which is illustrated with application to the ASCENDS mission for the measurement of CO<sub>2</sub> mixing ratios (XCO<sub>2</sub>).
Additional advantages of the method include the possibility to closely match cross-band weighting function
combinations which is harder to achieve using conventional differential absorption techniques and the potential for
additional corrections for water vapor and other interferences without using the data from numerical weather prediction
(NWP) models.

We present the performance of a single frequency, single-polarization holmium (Ho<sup>3+</sup>)-doped ZBLAN (ZrF<sub>4</sub>-BaF<sub>2</sub>-LaF<sub>3</sub>- AlF<sub>3</sub>-NaF) fiber laser at 1200 nm. This distributed Bragg reflector (DBR) fiber laser was developed by splicing a 22 mm long highly Ho<sup>3+</sup>-doped ZBLAN fiber to a pair of silica fiber Bragg gratings (FBG). The successful fusion splicing of silica fiber to ZBLAN fiber, with their very different melting temperatures, was accomplished by using NP Photonics proprietary splicing technique. The 3 mol% Ho<sup>3+</sup>-doped ZBLAN fiber had a core diameter of 6.5 &mu;m and a cladding diameter of 125 &mu;m. The threshold of this laser was seen to be about 260 mW, and when the pump power was 520 mW, the output power was about 10 mW. The efficiency of the 1200 nm single-frequency fiber laser, i.e. the ratio of the output power to the launched pump power, was about 3.8%. The linewidth of the 1200 nm single-frequency fiber laser was estimated to be about 100 kHz by comparing the measured frequency noise of the 1200 nm single-frequency fiber laser with that of 1 &mu;m NP Photonics single-frequency fiber lasers whose linewidths have been measured to be in the 1- 10 kHz range. The relative intensity noise of this DBR all-fiber laser was measured to be &lt; 110 dB/Hz at the relaxation oscillation peak and the polarization extinction ratio was measured to be &gt; 19 dB. Due to its low phonon energy and long radiative lifetimes, rare-earth-doped ZBLAN allows various transitions that are typically terminated in silica glass, resulting in ultraviolet, visible, and infrared rare-earth doped ZBLAN lasers. Therefore, our results highlight the exciting prospect that the accessible wavelength range of single-frequency DBR fiber lasers can be expanded significantly by using rare-earth-doped ZBLAN fibers.

We have carried out comparative simulation studies to establish the advantages and limitations of alternative spectral
regions and measurement wavelengths being investigated by different groups for the sensing of CO<sub>2</sub> and O<sub>2</sub> for potential
use in the ASCENDS mission implementation. Our studies are based on the lidar modeling framework we developed
specifically for ASCENDS which may be further applied to similar missions relying on the active sensing approach from
space or aircraft. The modeling framework performs standard lidar sensitivity calculations, and also includes analysis of
weighting functions and the effects of laser wavelength instabilities. As such, the factors considered in the analysis
include the general LIDAR sensitivity, shapes of the weighting functions, as well as the added error due to the laser
wavelength jitter in the selected spectral bands and wavelength regions. In particular, the studies were performed for the
1.26 – 1.27 micron and the A-band of oxygen, as well as the 1.57 and 2.06 micron bands of carbon dioxide.
Additionally, the analysis is based on a range of satellite datasets and models to also take into account a variety of spacial
and temporal variations in surface and atmospheric parameters. The results of our comparative studies for alternative
spectral bands will be presented including the quantitative estimates of required constraints on selected system
parameters to achieve the desired accuracy of ~0.3% in XCO<sub>2</sub> measurements.

The objective of the Materials International Space Station Experiment (MISSE) is to study the performance of novel materials when subjected to the synergistic effects of the harsh space environment for several months. MISSE missions provide an opportunity for developing space qualifiable materials. Several laser and lidar components were sent by NASA Langley Research Center (LaRC) as a part of the MISSE 7 mission. The MISSE 7 module was transported to the international space station (ISS) via STS 129 mission that was launched on Nov 16, 2009. Later, the MISSE 7 module was brought back to the earth via the STS 134 that landed on June 1, 2011. The MISSE 7 module that was subjected to exposure in space environment for more than one and a half year included fiber laser, solid-state laser gain materials, detectors, and semiconductor laser diode. Performance testing of these components is now progressing. In this paper, the current progress on post-flight performance testing of a high-speed photodetector and a balanced receiver is discussed. Preliminary findings show that detector characteristics did not undergo any significant degradation.

We review some of our recent results on frequency upconversion. Frequency upconversion of laser pulses at
10.26 &#956;m to those at 1.187 &#956;m was measured in the presence of Nd:YAG laser pulses based on difference-frequency
generation in a 10-mm-long GaSe crystal. The highest power conversion efficiency for the
parametric conversion was determined to be 20.9%, corresponding to the photon conversion efficiency of
2.42%. This value is two orders of magnitude higher than the highest value reported on GaSe in the
literature. The saturation of the output power at 1.187 &#956;m as the input power at 10.26 &#956;m was increased, due
to the back conversion, i.e. 1.187 &#956;m + 10.26 &#956;m &rarr; 1.064 &#956;m, was clearly evidenced. Besides the midinfrared
region, we have also investigated frequency upconversion of the input signals at 1.27 &#956;m and 1.57
&#956;m in the presence of the pump beam at 1.064 &#956;m in bulk periodically-poled LiNbO<sub>3</sub> (PPLN) crystals. The
quantum efficiencies of 11.2% and 13.2% have been achieved at these two input wavelengths. The
detections of low-level photons at these two wavelengths are important to the NASA Active Sensing of CO<sub>2</sub>
Emissions over Nights, Days, and Seasons (ASCENDS) mission.

In this paper, development of single crystalline n- and p- type PbTe crystals and PbTe bulk nanocomposites using PbTe
nano powders and emerging field assisted sintering technology (FAST) are discussed. Materials requirements for efficient
thermoelectric power generation using waste heat at intermediate temperature range (6500 to 8500 K) will be discussed.
Recent results on production of n- and p- type PbTe crystals and their thermoelectric characterization will be presented.
Relative characteristics and performance of PbTe bulk single crystals and nano composites for thermoelectric power
generation will be discussed.

The National Research Council's (NRC) Decadal Survey (DS) of Earth Science and Applications from Space has
identified the Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) as an important
atmospheric science mission. NASA Langley Research Center, working with its partners, is developing fiber laser
architecture based intensity modulated CW laser absorption spectrometer for measuring XCO2 in the 1571 nm spectral
band. In support of this measurement, remote sensing of O2 in the 1260 nm spectral band for surface pressure
measurements is also being developed. In this paper, we will present recent progress made in the development of
advanced transmitter modules for CO<sub>2</sub> and O<sub>2</sub> sensing. Advanced DFB seed laser modules incorporating low-noise
variable laser bias current supply and low-noise variable temperature control circuit have been developed. The 1571 nm
modules operate at &gt;80 mW and could be tuned continuously over the wavelength range of 1569-1574nm at a rate of 2
pm/mV. Fine tuning was demonstrated by adjusting the laser drive at a rate of 0.7 pm/mV. Heterodyne linewidth
measurements have been performed showing linewidth ~200 kHz and frequency jitter ~75 MHz. In the case of 1260 nm
DFB laser modules, we have shown continuous tuning over a range of 1261.4 - 1262.6 nm by changing chip operating
temperature and 1261.0 - 1262.0 nm by changing the laser diode drive level. In addition, we have created a new laser
package configuration which has been shown to improve the TEC coefficient of performance by a factor of 5 and
improved the overall efficiency of the laser module by a factor of 2.

The Active Sensing of CO2 Emissions over Nights Days and Seasons (ASCENDS) mission recommended by the
NRC Decadal Survey has a desired accuracy of 0.3% in carbon dioxide mixing ratio (XCO2) retrievals requiring careful
selection and optimization of the instrument parameters. NASA Langley Research Center (LaRC) is investigating 1.57
micron carbon dioxide as well as the 1.26-1.27 micron oxygen bands for our proposed ASCENDS mission requirements
investigation. Simulation studies are underway for these bands to select optimum instrument parameters. The
simulations are based on a multi-wavelength lidar modeling framework being developed at NASA LaRC to predict the
performance of CO<sub>2</sub> and O<sub>2</sub> sensing from space and airborne platforms. The modeling framework consists of a lidar
simulation module and a line-by-line calculation component with interchangeable lineshape routines to test the
performance of alternative lineshape models in the simulations. As an option the line-by-line radiative transfer model
(LBLRTM) program may also be used for line-by-line calculations. The modeling framework is being used to perform
error analysis, establish optimum measurement wavelengths as well as to identify the best lineshape models to be used in
CO<sub>2</sub> and O<sub>2</sub> retrievals. Several additional programs for HITRAN database management and related simulations are
planned to be included in the framework. The description of the modeling framework with selected results of the
simulation studies for CO<sub>2</sub> and O<sub>2</sub> sensing is presented in this paper.

Holmium (Ho<sup>3+</sup>)-doped ZBLAN glasses have been investigated for the purpose of achieving efficient fiber lasers at
1.2 &mu;m. Because of the long lifetime of the upper laser level and the small phonon energy in Ho<sup>3+</sup>-doped ZBLAN
glasses, strong fluorescence at 1.2 &mu;m that usually cannot be observed in Ho-doped silica glass has been measured.
Fluorescence of 1 mol%, 3 mol%, and 6 mol% Ho<sup>3+</sup>-doped ZBLAN glasses are reported. The effect of cerium and
terbium ions on the emission of Ho<sup>3+</sup>-doped ZBLAN glass has also been studied. Obstacles to achieving an efficient
Ho<sup>3+</sup>-doped ZBLAN laser are analyzed and discussed. In studies of a commercial Ho<sup>3+</sup>-doped ZBLAN fiber laser, it was
found that the 3 &mu;m four-energy-level laser can easily overwhelm the 1.2 &mu;m laser, which is a three-energy-level system
having the same upper laser level with the 3 &mu;m laser. In order to effectively suppress the competiting 3 &mu;m transition,
advanced Ho<sup>3+</sup>-doped ZBLAN fiber has been designed and fabricated for 1.2 &mu;m fiber lasers. Fiber lasers at 1.2 &mu;m
using the new Ho<sup>3+</sup>-doped ZBLAN fiber have been developed. Our experiments demonstrate that the new Ho<sup>3+</sup>-doped
ZBLAN fiber is an efficient gain medium for lasers at 1.2 &mu;m.

The key objective of this article is to underscore that as engineers, we need to pay close attention in repeatedly validating
and re-validating the underlying physical processes behind a working theory that models a phenomenon we are using to
create tools and technologies. We use the test case, the prevailing mode-lock theory, to illustrate our views by identifying
existing contradictions and showing approach towards their resolution by identifying the relevant physical processes.
The current theory tells us that the Fourier summation of all the allowed cavity modes directly produces the train of
pulses. It effectively assumes that electromagnetic (EM) waves are capable of re-organizing their spatial and temporal
energy distribution to generate a train of temporal pulses while preserving the spatial mode energy distribution. The
implication is that EM waves interact with each other by themselves. Even though the theory is working, we have three
logical problems. First, in the real world, in the linear domain, waves never interact with each other. On careful analysis
of all types of interference experiments, we will recognize that only in the presence of some interacting material medium
can we observe the physical superposition EFFECT. In other words, detectors carryout the superposition effect we call
interference phenomenon, through the summation of their multiple simultaneous linear stimulations and then absorbing
energy proportional to the square modulus of the sum total stimulation. Second, a Fourier monochromatic wave, existing
in all space and time, is a non-causal hypothesis. Just because our theories are working does not mean that we have
understood the real physical interaction processes in nature. We need to build our theories based upon space and time
finite EM wave packet containing a finite amount of energy, which is a causal approach. Third, in spite of staggering
successes of Quantum Mechanics, we do not yet have a self consistent model for space and time finite model of a
photon. QM only predicts that EM energy emission (spontaneous and stimulated) takes place only in a discrete amount at
a time from atoms and molecules. It does not give us recipe about how to visualize a propagating photon as it expands
diffractively. However, Huygens-Fresnel's classical diffraction integral gives us a rigorous model, which is the
cornerstone of modeling evolution of laser cavity modes, CW or pulsed. In this paper, we highlight the contradictions
that arise out of the prevailing mode-lock theory and resolve them by using causal models, already underscored above.
For example, there are now a wide range of very successful technological applications of the frequency comb extracted
out of fs lasers. If the Fourier summation were the correct physical process, then all the cavity modes would have been
summed (converted) into a single mean frequency around the gain line center for perfectly mode-locked systems.
Further, sending such fs pulses through an optical spectrometer would have always displayed a transform limited fringe,
centering on the mean Fourier frequency, rather than generating the comb frequencies, albeit instrumentally broadened.
Output pulse train from a phase locked laser is functionally produced due to the oscillatory time-gating behavior of the
intra-cavity phase-locking devices. So, we need to pay more attention to the fast temporal behavior of the materials we
use for achieving very fast time-gating, since this material imposes phase locking on the cavity modes to enhance its own
high-contrast time-gating behavior.

NASA Langley Research Center is working on a continuous wave (cw) laser-based remote sensing scheme for the detection of CO2 and O2 from space-based platforms suitable for an active sensing of CO2 emissions over nights, days, and seasons (ASCENDS) mission. ASCENDS is a future space-based mission to determine the global distribution of sources and sinks of atmospheric carbon dioxide (CO2). A unique, multifrequency, intensity modulated cw laser absorption spectrometer operating at 1.57 μm for CO2 sensing has been developed. Effective aerosol and cloud discrimination techniques are being investigated in order to determine concentration values with accuracies less than 0.3%. In this paper, we discuss the demonstration of a pseudonoise code-based technique for cloud and aerosol discrimination applications. The possibility of using maximum length sequences for range and absorption measurements is investigated. A simple model for accomplishing this objective is formulated. Proof-of-concept experiments carried out using a sonar-based LIDAR simulator that was built using simple audio hardware provided promising results for extension into optical wavelengths.

A reviewing of many published experimental and theoretical papers demonstrate that the resolving powers of microscopes, spectroscopes and telescopes can be enhanced by orders of magnitude better than old classical limits by various advanced techniques including de-convolution of the CW-response function of these instruments. Heisenberg's original analogy of limited resolution of a microscope, to support his mathematical uncertainty relation, is no longer
justifiable today. Modern techniques of detecting single isolated atoms through fluorescence also over-ride this generalized uncertainty principle. Various nano-technology techniques are also making atoms observable and location precisely measurable. Even the traditional time-frequency uncertainty relation or bandwidth limit &delta;<i>v</i>&delta;<i>t</i> &ge; 1 can be circumvented while doing spectrometry with short pulses by deriving and de-convolving the pulse-response function of the spectrometer just as we do for CW input.

We present an approach to demonstrate the Non-Interaction of Waves (NIW)-principle by showing that dark fringes in the near-field Talbot diffraction patterns are not devoid of energy. We believe that a detector is simply incapable of absorbing any energy at the dark fringe locations simply because the resultant of the induced stimulations on a local detecting dipole due to all the E-vectors is zero. The joint stimulation is strongest at the bright fringe locations. The amplitude (& hence potentially detectable energy) flow through the "dark fringe locations" is demonstrated by
obstructing the "bright fringe" locations at the half-Talbot plane with an identical grating that generated this diffraction image. Then, by propagating the transmitted complex amplitudes through the dark fringes, we would like to show that the Talbot plane can still receive more energy than that could have been recorded out of those same dark fringe locations at the half Talbot plane.

This paper will present results of computer models depicting the evolution of diffractive processes through passive and
active cavities (traditional stable resonator and single mode fiber) as the number of passes (or the length of propagation)
increases. The objective is to visualize how the spatially stable eigen-modes evolve with propagation. Our core
assumptions are the validity of the Huygens-Fresnel hypothesis of secondary wavelets and the recently articulated Non-
Interaction of Waves (NIW) principle in this conference series. The NIW-principle implies that even the diffracted
secondary wavelets propagate conjointly but without re-arranging their spatial energy distribution unless one inserts
some interacting material medium within the diffracting beam. Accordingly, we anticipate that the evolution of the
measurable energy distribution in the diffraction pattern will be different in the presence of gain medium whose gain
profile varies in the direction orthogonal to the cavity axis. We also anticipate that a cavity with high gain profile will
generate the stable spatial eigen-mode with a fewer number of passes through the cavity than with lower gain, or no
gain. We will also present the mode evolution process when the seed signal is a pulse of length that is shorter than that of
the cavity. We believe this paper will provide useful insights to the students who are introduced to the concept of
spatially well defined Gaussian laser modes for the first time.

In this paper, progress made so far in the performance testing of waveguide laser components sent by NASA Langley
Research Center on MISSE 6 mission will be discussed. The objective of the Materials International Space Station
Experiment (MISSE) is to study the performance of novel materials when subjected to the synergistic effects of the
harsh space environment for several months. MISSE missions provide an opportunity for developing space qualifiable
materials. The results of post-testing of several optical materials that were recently returned back after more than one
year of exposure on the International Space Station (ISS) will be presented. The items were part of the MISSE 6 mission
that was transported to the ISS via STS 123 on March 11, 2008 and returned to the Earth via STS 128 that was launched
on August 2009. The materials experienced no visible damage during lengthy exposure in space. In the case of laser
diode, a comparison of elemental analysis with pre-flight conditions will be presented. Furthermore, the optical
components sent on MISSE 7 mission via STS-129 and later retrieved by STS-134 will be briefly discussed.

NASA Langley Research Center is working on a continuous wave (CW) laser based remote sensing scheme for the
detection of CO<sub>2</sub>and O<sub>2</sub> from space based platforms suitable for ACTIVE SENSING OF CO<sub>2</sub> EMISSIONS OVER
NIGHTS, DAYS, AND SEASONS (ASCENDS) mission. ASCENDS is a future space-based mission to determine the
global distribution of sources and sinks of atmospheric carbon dioxide (CO<sub>2</sub>). A unique, multi-frequency, intensity
modulated CW (IMCW) laser absorption spectrometer (LAS) operating at 1.57 micron for CO<sub>2</sub> sensing has been
developed. Effective aerosol and cloud discrimination techniques are being investigated in order to determine
concentration values with accuracies less than 0.3%. In this paper, we discuss the demonstration of a PN code based
technique for cloud and aerosol discrimination applications. The possibility of using maximum length (ML)-sequences
for range and absorption measurements is investigated. A simple model for accomplishing this objective is formulated,
Proof-of-concept experiments carried out using SONAR based LIDAR simulator that was built using simple audio
hardware provided promising results for extension into optical wavelengths.

NASA Langley Research Center (LaRC) is working on a prototype laser system for simultaneous
measurement of CO<sub>2</sub> and O<sub>2</sub> for planned Active Sensing of CO<sub>2</sub> Emissions over Nights, Days, and
Seasons (ASCENDS) mission application. For this purpose, 1571 nm spectral band for CO<sub>2</sub> sensing
and 1262 nm spectral band for oxygen sensing have been selected. In this paper, we discuss recent
progress made in the development of single mode, compact and stable, seed laser technologies for
CO<sub>2</sub> and O<sub>2</sub> transmitters. In particular, the development of an advanced distributed feedback laser
(DFB) module master oscillator operating at 1571 nm, that is efficiently coupled to drive electronics
and nano-cooling scheme in a single hermetically sealed package of volume less than 2" x 2" x 0.5", is presented.

Materials International Space Station Experiment (MISSE) missions provide an opportunity for developing space
qualifiable materials by studying the response of novel materials when subjected to the synergistic effects of the harsh
space environment. MISSE 6 was transported to the international Space Station (ISS) via STS 123 on March 11. 2008.
The astronauts successfully attached the passive experiment containers (PEC) to external handrails of the international
space station (ISS) and opened up for long term exposure. After more than a year of exposure attached to the station's
exterior, the PEC with several hundred material samples returned to the earth with the STS-128 space shuttle crew that
was launched on shuttle Discovery from the Kennedy Space Center, Fla., on Aug. 28. Meanwhile, MISSE 7 launch is
scheduled to be launched on STS 129 mission. MISSE-7 was launched on Space Shuttle mission STS-129 on Atlantis
was launched on November 16, 2009. This paper will briefly review recent efforts on MISSE 6 and MISSE 7 missions
at NASA Langley Research Center (LaRC).

We review our previous results on frequency upconversion. Frequency upconversion of laser pulses at 10.26
&#956;m to those at 1.187 &mu;m was measured in the presence of Nd:YAG laser pulses based on differencefrequency
generation in a 10-mm-long GaSe crystal. The highest power conversion efficiency for the
parametric conversion was determined to be 20.9%, corresponding to the photon conversion efficiency of
2.42%. This value is two orders of magnitude higher than the highest value reported on GaSe in the
literature. The saturation of the output power at 1.187 &mu;m as the input power at 10.26 &mu;m was increased, due
to the back conversion, i.e. 1.187 &mu;m + 10.26 &mu;m &rarr; 1.064 &mu;m, was clearly evidenced. Besides the midinfrared
region, we have also investigated frequency upconversion of the input signals at 1.27 &mu;m and 1.57
&mu;m in the presence of the pump beam at 1.064 &mu;m in bulk periodically-poled LiNbO<sub>3</sub> (PPLN) crystals. The
quantum efficiencies of 11.2% and 13.2% have been achieved at these two input wavelengths. The
detections of low-level photons at these two wavelengths are important to the NASA Active Sensing of CO<sub>2</sub>
Emissions over Nights, Days, and Seasons (ASCENDS) mission.

We report the results of fabrication and testing of a thermoelectric power generation module. The
module was fabricated using a new "flip-chip" module assembly technique that is scalable and
modular. This technique results in a low value of contact resistivity ( &le; 10<sup>5</sup> &Omega;-cm<sup>2</sup> ). It can be used to leverage new advances in thin-film and nanostructured materials for the fabrication of new
miniature thermoelectric devices. It may also enable monolithic integration of large devices or tandem arrays of devices on flexible or curved surfaces. Under mild testing, a power of 22 mW/cm<sup>2</sup> was obtained from small (&lt;100 K) temperature differences. At higher, more realistic temperature differences, ~500 K, where the efficiency of these materials greatly improves, this power density would scale to between 0.5 and 1 Watt/cm<sup>2</sup>. These results highlight the excellent potential for the generation and scavenging of electrical power of practical and usable magnitude for remote applications using thermoelectric power generation technologies.

Photons are non-interacting entities. Light beams do not interfere by themselves. Light beams constituting
different laser modes (frequencies) are not capable of re-arranging their energies from extended timedomain
to ultra-short time-domain by themselves without the aid of light-matter interactions with suitable
intra-cavity devices. In this paper we will discuss the time-gating properties of intra-cavity "mode-locking"
devices that actually help generate a regular train of high energy wave packets.

Formulations for second and higher harmonic frequency up & down conversions, as well as multi photon processes directly assume
summability and divisibility of photons. Quantum mechanical (QM) interpretations are completely congruent with these assumptions.
However, for linear optical phenomena (interference, diffraction, refraction, material dispersion, spectral dispersion, etc.), we have a
profound dichotomy. Most optical engineers innovate and analyze all optical instruments by propagating pure classical
electromagnetic (EM) fields using Maxwell's equations and gives only 'lip-service' to the concept "indivisible light quanta". Further,
irrespective of linearity or nonlinearity of the phenomena, the final results are always registered through some photo-electric or
photo-chemical effects. This is mathematically well modeled by a quadratic action (energy absorption) relation. Since QM does not
preclude divisibility or summability of photons in nonlinear & multi-photon effects, it cannot have any foundational reason against
these same possibilities in linear optical phenomena. It implies that we must carefully revisit the fundamental roots behind all lightmatter
interaction processes and understand the common origin of "graininess" and "discreteness' of light energy.

The objective of the Materials International Space Station Experiment (MISSE) is to study the performance of novel
materials when subjected to the synergistic effects of the harsh space environment for several months. MISSE missions
provide an opportunity for developing space qualifiable materials. Two lasers and a few optical components from
NASA Lnagley Research Center (LaRC) were included in the MISSE 6 mission for long term exposure. MISSE 6 items
were characterized and packed inside a ruggedized Passive Experiment Container (PEC) that resembles a suitcase. The
PEC was tested for survivability due to launch conditions. MISSE 6 was transported to the international Space Station
(ISS) via STS 123 on March 11. 2008. The astronauts successfully attached the PEC to external handrails of the ISS and
opened the PEC for long term exposure to the space environment. The current plan is to bring the MISSE 6 PEC back to
the Earth via STS 128 mission scheduled for launch in August 2009. Currently, preparations for launching the MISSE 7
mission are progressing. Laser and lidar components assembled on a flight-worthy platform are included from NASA
LaRC. MISSE 7 launch is scheduled to be launched on STS 129 mission. This paper will briefly review recent efforts
on MISSE 6 and MISSE 7 missions at NASA Langley Research Center (LaRC).

The objective of the Materials International Space Station Experiment (MISSE) is to study the performance of novel
materials when subjected to the synergistic effects of the harsh space environment for several months. In this paper, a
few laser and optical elements from NASA Langley Research Center (LaRC) that have been flown on MISSE 6 mission
will be discussed. These items were characterized and packed inside a ruggedized Passive Experiment Container (PEC)
that resembles a suitcase. The PEC was tested for survivability due to launch conditions. Subsequently, the MISSE 6
PEC was transported by the STS-123 mission to International Space Station (ISS) on March 11, 2008. The astronauts
successfully attached the PEC to external handrails and opened the PEC for long term exposure to the space
environment. The plan is to retrieve the MISSE 6 PEC by STS-128 mission in August 2009.

Polycrystalline ceramic laser materials are gaining importance in the development of novel diode-pumped solid-state
lasers. Compared to single-crystals, ceramic laser materials offer advantages in terms of ease of fabrication, shape, size,
and control of dopant concentrations. Recently, we have developed Neodymium doped Yttria (Nd:Y<sub>2</sub>O<sub>3</sub>) as a solid-state
ceramic laser material. A scalable production method was utilized to make spherical non agglomerated and
monodisperse metastable ceramic powders of compositions that were used to fabricate polycrystalline ceramic material
components. This processing technique allowed for higher doping concentrations without the segregation problems that
are normally encountered in single crystalline growth. We have successfully fabricated undoped and Neodymium doped
Yttria material up to 2" in diameter, Ytterbium doped Yttria, and erbium doped Yttria. We are also in the process of
developing other sesquioxides such as scandium Oxide (Sc<sub>2</sub>O<sub>3</sub>) and Lutesium Oxide (Lu<sub>2</sub>O<sub>3</sub>) doped with Ytterbium,
erbium and thulium dopants. In this paper, we present our initial results on the material, optical, and spectroscopic
properties of the doped and undoped sesquioxide materials. Polycrystalline ceramic lasers have enormous potential
applications including remote sensing, chem.-bio detection, and space exploration research. It is also potentially much
less expensive to produce ceramic laser materials compared to their single crystalline counterparts because of the shorter
fabrication time and the potential for mass production in large sizes.

Non-interacting Boson-like properties of light beams imply that superposed light beams by themselves cannot re-organize or re-distribute
their energies either in spatial or in the time domain. Yet, we explain short pulse generation by lasers with intra-cavity
devices as due to phase locking of the longitudinal modes of the laser cavity, irrespective of whether the lasing material has
homogeneously or in-homogeneously broadened spectral characteristics. Most short pulse generating "mode locked" lasers use
homogeneously broadened gain media that always tend to run in a single frequency at the gain line center that has the highest gain
under CW condition. Can a passive intra-cavity saturable absorber or a Kerr medium switch the spectral characteristics of a
homogeneously broadened gain medium into an in-homogeneously broadened gain medium to make the laser run in multiple
longitudinal modes? We believe that the lasing medium runs in a single mode (frequency) at the center of the gain medium and the
intra-cavity saturable absorber or the Kerr medium simply plays the role of fast time gating (switching). This implies that "transform
limited" "mode-locked" laser pulses, in reality, contain only a single carrier frequency. We will present the appropriate mathematical
representation for the spectral analysis of such "mode-locked" pulses. We will also discuss models for the physical process that give
rise to the generation of short (nanosecond class) pulses even in the absence of multiple longitudinal modes and then use the concepts
for generating shorter (picosecond and femtosecond) pulses.

The objective of the Materials International Space Station Experiment (MISSE) is to study the performance of novel
materials when subjected to the synergistic effects of the harsh space environment for several months. In this paper, a
few materials and components from NASA Langley Research Center (LaRC) that have been flown on MISSE 6 mission
will be discussed. These include laser and optical elements for photonic devices. The pre-characterized MISSE 6
materials were packed inside a ruggedized Passive Experiment Container (PEC) that resembles a suitcase. The PEC was
tested for survivability due to launch conditions. Subsequently, the MISSE 6 PEC was transported by the STS-123
mission to International Space Station (ISS) on March 11, 2008. The astronauts successfully attached the PEC to
external handrails and opened the PEC for long term exposure to the space environment. The plan is to retrieve the
MISSE 6 PEC by STS-128 mission in 2009.

Satellite and space-based applications of photonic devices and systems require operational reliability in the harsh
environment of space for extended periods of time. This in turn requires every component of the systems and their
packaging to meet space qualifications. Acousto- and electro-optical devices form the major components of many
current space based optical systems, which is the focus of this paper. The major space qualification issues are related to:
mechanical stability, thermal effects and operation of the devices in the naturally occurring space radiation environment.
This paper will discuss acousto- and electro-optic materials and devices with respect to their stability against mechanical
vibrations, thermal cycling in operating and non-operating conditions and device responses to space ionizing and
displacement radiation effects. Selection of suitable materials and packaging to meet space qualification criteria will also
be discussed. Finally, a general roadmap for production and testing of acousto- and electro-optic devices will be
discussed.

Any superposition effect as measured (SEM) by us is the summation of simultaneous stimulations
experienced by a detector due to the presence of multiple copies of a detectee each carrying different values
of the same parameter. We discus the cases with light beams carrying same frequency for both diffraction
and multiple beam Fabry-Perot interferometer and also a case where the two superposed light beams carry
different frequencies. Our key argument is that if light really consists of indivisible elementary particle,
photon, then it cannot by itself create superposition effect since the state vector of an elementary particle
cannot carry more than one values of any parameter at the same time. Fortunately, semiclassical model
explains all light induced interactions using quantized atoms and classical EM wave packet. Classical
physics, with its deeper commitment to Reality Ontology, was better prepared to nurture the emergence of
Quantum Mechanics and still can provide guidance to explore nature deeper if we pay careful attention to
successful classical formulations like Huygens-Fresnel diffraction integral.

NASA is developing state-of-the-art, all-solid-state, conductively cooled, diode-pumped, single longitudinal mode, tunable, short-pulsed, and high energy UV transmitters for ozone sensing measurements based on the Differential Absorption Lidar (DIAL) technique. The goal is to demonstrate output pulse energies greater than 200 mJ at pulse repetition frequencies of 10 Hz to 50 Hz, and pulsewidths in the range of 10 ns to 25 ns at UV wavelengths of 308 nm to 320 nm. The proposed scheme is to utilize the robust Nd:YAG pump laser technology in combination with nonlinear optics arrangement comprising of a novel optical parametric oscillator (OPO) and a sum frequency generator (SFG) to generate required UV wavelengths. In this paper, recent results of the development of Nd:YAG pump laser and UV converter module are presented. At 1064 nm, an output pulse energy of 1020 mJ at 16 ns pulsewidth and 50 Hz PRF yielding greater than 7% wall plug efficiency has been demonstrated. With improved drive electronics, this pump laser has the potential to generate greater than 1.2 J/pulse. The refined OPO module to aid in the generation of >200 mJ/pulse of UV radiation is also presented. The UV transmitters are being designed for DIAL operation under strong daylight conditions from space based platforms.

Q-switching techniques that modify the quality factor of a laser resonator are normally used to generate short pulses in a solid-state laser. The saturable absorber based technique, also known as passive Q-switching, is operationally attractive and simple when compared with mechanical or active optical techniques. Cr4+:YAG is a common saturable absorber material for many laser materials including Nd:YAG for operation around 1 &#956;m wavelength. Recently, self-passive Qswitching using a Nd:YAG gain medium that is externally implanted with chromium ions through annealing process has been demonstrated. Pulsewidths up to 2&#956;secs and PRFs up to 100kHz have been demonstrated. In this paper, the improved annealing technique utilized to obtain chromium doped Nd:YAG crystals is discussed. Tailored dopant chromium ion profile inside a host laser material is shown to provide controlled temporal lasing characteristics. The
current technique is applicable to several other laser gain media. The present technique simplifies laser cavity configuration, eliminates alignment issues that could exist between the gain medium and passive Q-switch crystal, and aids in the rugged packaging of a laser module.

Chemical and biological (Chem-Bio) sensors for detection and tracking of hazardous and toxic agents are primarily being developed for homeland security and defense applications at various government laboratories and research institutions. However, several groups at NASA and various universities are working on similar sensors for space-based applications. The quest for answers to questions on the origins of life on the Martian enironment is continuing at NASA. Recent studies on a Martian meteorite have kindled interest in the possibilities of past life on Mars. The existance of polycyclic aromatic hydrocarbons in fresh fracture surfaces have promoted further studies to examine the evidence for possibilities of the existenc of life on Martian surface soil in the past. Lignins and kerogens containing aromatic and polyaromatic components which are considered precursors of life on Mars. Likwise, tholins are considered
possible precurors for life on some outerbodies in our Solar system. Laser induced Fluorescence (LIF) and Raman based techniques with emphasis in the deep ultraviolet (UV) (200-300 nm) spectral region are anticipated to play a significant role in characterizing these precursors. In this paper, previous stuides done on these precursors in the UV are examined for the development of a wavelength agile LIF system for in situ and remote sensing experiments in the deep-UV
spectral region.

High power solid state tunable lasers have played an important role in providing the technology necessary for active remote sensing and would be very useful for space exploration. Many recent studies on diode-pumped solid state lasers have focused on polycrystalline ceramic lasers. We present our initial results on the material, optical, and spectroscopic properties of a solid-state ceramic laser material using neodymium doped Yttria (Nd:Y2O3). Using a proprietary scalable production method, spherical non agglomerated and monodisperse ceramic powders of Nd:Y2O3 are made that can be used to fabricate polycrystalline ceramic material disks with sintered grain size in a suitable range. Initially, we produced translucent material with good emission properties. In further studies we have successfully prepared transparent Nd:Yttria ceramic material. Polycrystalline ceramic lasers have enormous potential commercial applications, which include remote sensing, chemical detection and space exploration research. Furthermore, the cost to produce ceramic laser materials is potentially much lower than that for single crystal materials because of the shorter time it takes to fabricate the material and also because of the possibility of mass production. The polycrystalline ceramic material that we have produced will be characterized for its suitability as a diode pumped solid state laser. Different laser designs will be discussed including end-pumping schemes and the thin-disk laser configuration.

Controlling/monitoring the thickness of applied paint in real time is important to many situations including painting ship and submarine hulls in dry docks for maintaining health of ships and submarines against the harshness of the sea, in automobile and aerospace industries, and in a variety of other industries as a control sensor that plays significant role in product quality, process control, and cost control. Insufficient thickness results to inadequate protection while overspray leads to waste and pollution of the environment. A rugged instrumentation for the real time non-contact accurate measurement of wet and dry paint film thickness measurement will be immensely valuable. As paint is applied with several layers of the same or different type, thickness of each newly sprayed wet layer is of most interest, but measurement on dry paint is also useful. In this study, we use acousto-optic tunable filter-based near infrared spectrometer to obtain the absorption spectrum of layers of paint sprayed on sand blasted steel surface and thus measure the thickness of coating under both wet and dry situations. NIR spectra are obtained from 1100 to 2300 nm on four sample of different thickness of paint up to 127 micron. Partial least squares model built with the spectra shows good correlation with standard error of prediction within ~ 0.7 micron. Results indicate that the spectra also respond to the amount of organic solvent in the wet paint and can be used to monitor the degree of dryness of the paint in real time.

The development of an alumina-rich cobalt-doped spinel saturable absorber for the passive q-switching of 1530-1555 nm lasing is reported1. This optimized composition results in crystals with excellent dopant uniformity that are highly manufacturable. The crystal growth and materials characterization are described as well as initial passive qswitch testing of the material. The single crystals grown and investigated crystallized in the Fd3m space group and have the formula Mg<sub>1-x</sub>Co<sub>x</sub>Al<sub>y</sub>O<sub>z</sub> where x is greater than 0 and less than 1, y is greater than 2 and less than about 8, and z is between about 4 and 13. Comparison data of stoichiometric spinel MgAl<sub>2</sub>O<sub>4</sub> and alumina-rich non-stoichiometric spinel MgAl<sub>6</sub>O<sub>10</sub> are presented. The spinel lattice is comprised of octahedral and tetrahedral cationic sites, and in the alumina-rich spinel essentially all of the magnesium and cobalt occupy tetrahedral sites. The alumina-rich cobalt-doped spinel studied exhibited uniform cobalt-dopant distribution throughout the crystal and desirable mechanical and physical properties. Q-switched pulses were produced using the alumina-rich Co<sup>2+</sup>:MgAl<sub>6</sub>O<sub>10</sub> saturable absorber in a 980 nm diode-pumped Yb:Er:glass solid-state-laser operating at 1543 nm. The q-switching established employed the <sup>4</sup>T<sub>1</sub> absorption band of the Co<sup>2+</sup>: MgAl<sub>6</sub>O<sub>10</sub> and with quasi-CW pumping, pulsewidths greater than 20 ns, pulse energies of greater than 250 mJ, and free-running pulse repetition frequencies (PRFs) up to 1.2 kHz were demonstrated.

Laser based free-space-optical communication (FSOC) links are known to provide covert, secure, jam-proof and very
high bandwidth performances. For mobile platforms, precision pointing and tracking schemes are critical for continuous
guiding of a modulated laser beam to establish data link maintenance. In this paper, preliminary experiments of an
angle-discrimination based smart pointing and tracking scheme suitable for high-speed, closed-loop, FSOC is discussed.
A dual-axis, high-speed, galvo-mirror based scanner was utilized for conical scanning at 550 Hz. Greenwood frequency
in the presence of moderate atmospheric turbulence over a range of 1 km at 1.5 &mu;m was measured. It is shown that
selection of a scan frequency much higher than the Greenwood frequency reduces scintillation effects on scan angle
measurements for track loop maintenance. The measured scan angle value of the receiver with respect to transmit beam
when fed back to the scanner through an optical transponder would allow pointing error estimation and correction.
Based on our initial phenomenology study, it is shown that the scan-angle modulation based pointing and tracking
scheme would provide data-link reliability for dynamic platforms traveling on rough terrains.

In this paper, pulsed operation of the 980 nm diode-pumped Yb:Er:glass solid-state-laser operating at 1543 nm using Co:Spinel saturable absorber is described. The Yb:Er:glass gain medium was end-pumped using a 10 W fiber-coupled 980 nm laser diode. Passively q-switched laser operation was accomplished for both CW and quasi-CW operations. Up to 2 mm thick uncoated Co:Spinel samples were used for our tests. With quasi-CW pumping, pulsewidths greater than 20 ns, pulse energies of greater than 250 &mu;J and free-running PRFs up to 1.2 kHz have been demonstrated. So far, up to 3 % optical-to-optical efficiency has been achieved with uncoated q-switch materials. Currently, this laser is being developed for pumping a long-wave IR (8-12 &mu;m) optical parametric oscillator for use in spectrapolarimetric applications.

In this paper, the development of an active, wavelength agile, all-solid-state long-wave IR (8 - 12 &#956;m) spectrapolarimetric imager for extraction of Stokes vector is discussed. Results obtained in regard to the development of a Hg<sub>2</sub>Cl<sub>2</sub> based acousto-optic tunable filter and 1543 nm pumped AgGaSe<sub>2</sub> optical parametric oscillator are presented.

In this paper, the development of a compact, electronically tunable liquid crystal tunable retarder (LCTR) for manipulation of polarization is presented. A LCTR with one-inch aperture diameter has been designed and fabricated for operation over mid-wave IR (MWIR) spectral band. Using this device, quarter and half-wave retardation have been demonstrated at several prominent laser wavelengths in the
MWIR spectral region. Up to 74% efficiency has been demonstrated at 2.4 &mu;m wavelength. Highly efficient retarders are now being developed using perfluorinated liquid crystal mixtures. An LCTR is
anticipated to guide the development of a compact, wideband, and electronically tunable spectrapolarimetric imager.

A free-space, line-of-sight, ground-based optical link at 1.5 microns is attractive for tactical communications because it would provide eye-safety, covertness and jam-proof operation. However, the effects of atmospheric turbulence have to be appropriately mitigated for achieving acceptable bit-error-rate (BER) for reliable dissemination of information. Models to predict achievable BER at 1.5 microns for several beam propagation schemes that include beam scanning have been developed for various turbulence conditions. In this paper, we report performance characterization of free-space, high-data (>1Gb/s) rate beam propagation parameters at 1.5 microns for achieving BER reduction under the presence of turbulence. For standard free-space optical links, the mean SNR limits the achievable BER to lesser than 10-6 for Cn2 (structure constant of refractive index fluctuations) around 10-12 m-2/3. To validate these models, simultaneous measurements of structure constant of refractive index fluctuations, Cn2, and coherence diameter over tactical ranges have been carried out and analyzed. The effect of input beam conditioning to reduce BER levels have been explored. Furthermore, single and multiple transmit beams in conjunction with single and multiple detector arrangements have been examined. Based on these measurements, it is shown that the advantages of input beam conditioning coupled with modified receiver geometric characteristics would provide a path for BER reduction and hence, appreciable enhancements in data link reliability.

In this paper, the performance of a compact, eyesafe, all-solid-state, mid-wave IR (MWIR) transceiver for data communication through low visibility conditions is discussed. The transceiver was developed for Multiple Integrated Laser Engagement System (MILES) application. The MWIR wavelengths are derived using a passively q-switched Nd:YAG laser pumped periodically poled lithium niobate based optical parametric oscillator. MILES weapon code transmission for small and heavy weapon platforms have been demonstrated through dense theatrical fog. With 2 &#956;J/pulse at ~4 mm and a room temperature IR detector, greater than 5 km range has been successfully demonstrated. A bit map image transmission at MWIR wavelengths was also accomplished using this device. Test images consisting of 50x40 pixels and 100x80 pixels were successfully transmitted through free space.

The Army's objective is to design, develop and demonstrate its 'ability to distribute information around the battlefield.' Future Army systems will be based on a survivable, adaptable network capable of integrating commercial services and securely utilizing bandwidth for voice, data, and video applications. However, microwave bandwidth allocation has been a serious problem (given crosstalk, interference and frequency management) for a mobile, adaptive communication network. Because of the inherent advantages of the high data rate, crosstalk independence, jam - resistance, covertness and quick system setup time, the Army is looking into optical wireless communication as a means to address this communications requirement. However, development of a fielded laser communication system requires the development of enabling technologies, the understanding of physical limits and performance, and concept of operations (CONOPS).

High power laser based electro-optic sensor systems are generally bulky. Currently, several of these systems have to be located near exit apertures on airborne platforms due to lack of high damage resistant flexible optical conduits offering high mode fidelity and transmission efficiency. In several cases, system functionality has to be scaled down in a space-constrained environment. Coherent Technologies, Inc. has developed flexible, efficient, metallic rectangular hollow waveguides for use with high-energy laser systems such that they can be re-located to a convenient, safe, and protective location. These ribbon-like waveguides provide &gt;96%/m transmission efficiency with near diffraction-limited performance and high mode fidelity besides transporting high-energy optical radiation. In this paper, damage threshold measurement carried out using aluminum based rectangular hollow waveguides is reported. Measurements at 2 micrometers and 10.6 micrometers wavelengths in 1-m long waveguides with aperture heights of 100 to 250 micrometers have been performed. Damage thresholds greater than 1 GW/cm<SUP>2</SUP> has been measured at 2 micrometers wavelength. Being thin and flexible, these waveguides are low cost, easy to fabricate, and are amenable for integration into fuselage of an airplane. It is anticipated that distributed aperture coherent ladar systems and high power optical directed energy on space/airborne platforms would benefit from this technology.

Maintenance of laser beam alignment in optical systems is highly desirable for effective operation. In this paper, a LCTV-based alignment preserving scheme is discussed. We show that a laser beam can be aligned automatically to an accuracy of less than plus or minus 2 micrometer using a LCTV with an average pixel pitch of 85 micrometer. Due to simplicity and low cost, the proposed scheme is attractive for use in laser based optical systems that are used on airborne platforms.

Recently, lasing action and subsequent optical parametric oscillation has been demonstrated inside a single crystal of Nd:MgO:LiNbO<SUB>3</SUB> that is pumped by semiconductor diodes. This device, known as OPOL (Optical Parametric Oscillator/Laser), is a highly efficient, continuously tunable coherent optical source that can generate near and mid-IR wavelengths in a compact unit. An OPAL (Optical Parametric Amplifier/Laser) is a similar device that can amplify weak signals. AN OPOL can be used to generate eyesafe wavelengths whereas an OPAL can be used to amplify weak return signals, and in combination can provide eye-safe operation, effective range enhancement and wavelength agility in a range finder. The AN/GVS-5 is a hand-held range finder that is powered by a 24 V dc battery, and uses a flash lamp pumped Nd:YAG laser operating at 1064 nm for its operation to provide a maximum range of 10 km. In this paper, the design of a battery operated OPOL and OPAL is presented, and their application in retrofitting the AN/GVS5 unit to provide eyesafe and wavelength agile operation is discussed.

In this paper, a fuzzy logic based approach to the cooling of laser materials is presented. The controller design is based on the performance characteristics of commercially available thermoelectric coolers. Simulation results are presented and discussed. The feasibility of implementing such a controller is evaluated.

Diagnoses of cancers and pulmonary embolism are performed by visually interpreting medical data on computer graphics displays. Interpretation aids for medical diagnosis and treatment are not available. The optical information processor system presented in this paper can be used as a second opinion in detecting cancers and classifying images; the final diagnosis is made by a physician. The optical information processing system uses a novel spatial multiplexing technique that allows several images to be processed simultaneously using the same spatial light modulator. Simulation results for liquid crystal display operated in a novel amplitude coupled with binary phase mode is described. In addition, simulation results for a phase modulating micro-mirror spatial light modulator are presented. Results using clinical data show that the optical information processing system can yield a diagnosis rate of 86%.

The development of high resolution spectrophotometers and colorimeters, combined with its portability and large data processing abilities, has made the color evaluation process easier and faster. Although these instruments are very useful for rapid pass or fail color inspections in many industries such as, the automotive industry, textile industry, etc., the final decision depends primarily upon a subjective visual assessment. Besides spectral analysis, which is useful in colorant selection, the interrelationship between various environmental factors, metamerism, and texture and composition of the material (substrate), has made visual coordination an acceptable methodology to obtain a repeatable finish and color quality. Subjective assessment in color matching, especially in colors that closely resemble one another, leads to laborious and time consuming adjustments that have to be performed to obtain the right concentration of the colorants. Color evaluation and color mixing for a given material surface are interdependent. Although there are analytical methods that provide a means for colorant analysis, their application is cumbersome and involves complex calculations. In this paper we develop a fuzzy approach to obtain optimal color correlation between visual assessment, computed color differences, and colorant composition.

Imaging using optical parametric amplification (OPA) and optical parametric up-conversion has been performed since 1960s. Various problems associated with the pump laser, such as beam quality, size, weight, and power consumption, and optical quality of crystals have limited the utility of these techniques. While in recent times, new as well as good optical quality crystals with high damage resistance are being frown, there is a need to incorporate efficient laser pump configurations for developing field deployable imaging systems. Based on the development of a highly efficient and very compact semiconductor diode pumped OPO, the present paper discusses the design concepts of a self- pumped optical parametric amplifier and mixer for imaging using mid-IR wavelengths.

In this paper, it is shown that twisted nematic liquid crystal television display panels (LCTV's) can be used as programmable optical elements to demonstrate basic optical phenomena (e.g., interference and diffraction) in the student optics laboratory. The LCTV'S considered are pixelated with gray levels appropriately manipulated to generate an optical element by electrically addressing the LCTV using image processing software. Programmable optical elements such as single or multiple apertures and slits, gratings (amplitude and phase), apertures with programmable shape and size, phase objects (wavefronts), and programmable pupil functions such as anamorphic lenses, lenslet arrays, and spherical lenses with programmable size, focal length, and generalized pupil functions that include wavefront aberration functions are discussed and the methods used to generate them are described. It is demonstrated that the LCTV combines the merits of discrete optical elements and graphic user interface based software tools to provide a simple and inexpensive means to study optical elements.

In this paper we have demonstrated a wavelength tuning scheme using a twisted nematic liquid crystal based LCTV operated in an amplitude coupled binary phase mode for three wave mixing devices. A cosine chirp that is written on the LCTV by electrically addressing its pixels through a personal computer, functions as a programmable spherical lens. Deflection of the input beam is achieved by introducing tilt aberration on the lens. A spot resolution of less than 1.65 arcsec, and a steering range of 2 degrees at a wavelength of 632.8 nm were achieved by continuously varying the tilt coefficient of the lens. The potential advantages of this scheme are speed, compactness, operational ease, and power consumption.

In this paper, deflection and scanning of a HeNe beam by a programmable phase Fresnel lens written on a LCTV has been demonstrated. Translation and tilt aberration respectively produces coarse and fine deflection of the beam. The rapid translation of the lens function, time dependent variation of the magnitude of the tilt aberration, and a combination of these two methods are used to demonstrate laser beam scanning. In our experiments, using the wavefront tilt aberration a measurable scan deflection accuracy of less than 8 (mu) rad is achieved. Using the lens translation scheme the beam is scanned over a 0.8 cm X 0.8 cm area at a distance of 50 cm. The scan time of the current system is limited by the standard video frame rate of the existing LCTV drive electronics. The performance limits of the LCTV-based deflection and scanning system are compared with those of acousto-optic deflectors and scanners.

This report summarizes the Threat Object Map (TOM) handover analysis that the ODA team has performed during the past year. The areas of study include evaluating data from the STORM 4 and STORM 6 missions to determine: (1) performance of a radar to optical interceptor TOM handover, (2) sensitivities to data latency both above and within the atmosphere, (3) platform sensitivities to closely spaced objects, and (4) sensitivity to N objects handed up from the radar to M objects on the interceptor focal plane. This analysis is limited to metric only TOM handover and does not include generalized TOM evaluation. The analysis uses the OMEGA and TOMAHOC codes. OMEGA models the radar noising. TOMAHOC (Threat Object Map and Handover Code) performs the metric handover. TOMAHOC contains bias removal algorithms and a Sparse Munkre's algorithm.

The measurement of laser beam quality is of prime importance for various applications. M<SUP>2</SUP> factor has been widely accepted as a standard for characterizing the quality of real laser beams. The inaccuracies present in the specifications of resonator elements, variations occurring due to various competing physical processes inside the lasing medium, and offsets in the cavity configuration make the beam quality deviate from the desired value. Since the beam quality can be improved by manipulating the cavity parameters, fine tuning of mirror separation distance can offer considerable modification in the beam quality. In this paper, a fuzzy logic based controller to obtain and monitor desired laser beam characteristics for stable resonators is discussed. The simulation results indicate that the proposed fuzzy logic controller will dynamically adapt to real laser beams and can offer superior performance over conventional proportional-integral-derivative (PID) controllers. The principle advantage of the present approach is that it provides a versatile means for automatic control over the beam characteristics without relying on detailed mathematical modeling techniques.

The beam characteristics of a laser depend on various factors such as temperature, mechanical deficiencies of mounts, tolerance specifications, etc. As such, there is a tendency for the beam characteristics to deviate from the desired characteristics. This paper describes the development of a fuzzy-logic based controller to obtain and maintain specific output beam characteristics of an optical resonator.

An optical parametric oscillator (OPO) produces coherent optical radiation which is tunable over a wide range. In this paper, a novel technique for angle tuning an OPO by an acousto-optic Bragg cell is discussed. It is shown that the proposed scheme provides course as well as fine tuning of signal wavelengths with high speed, and hence is a promising alternative to the conventional tuning techniques.

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Journal of Applied Remote SensingJournal of Astronomical Telescopes Instruments and SystemsJournal of Biomedical OpticsJournal of Electronic ImagingJournal of Medical ImagingJournal of Micro/Nanolithography, MEMS, and MOEMSJournal of NanophotonicsJournal of Photonics for EnergyNeurophotonicsOptical EngineeringSPIE Reviews